feat: add Paralleler type.

Author: ghosind

parallel.go

@@ -48,86 +48,13 @@ func ParallelWithContext(
 
 // parallel runs the functions asynchronously with the specified concurrency.
 func parallel(parent context.Context, concurrency int, funcs ...AsyncFn) ([][]any, error) {
-	// the number of concurrency should be 0 (no limitation) or greater than 0.
-	if concurrency < 0 {
-		panic(ErrInvalidConcurrency)
-	}
-	validateAsyncFuncs(funcs...)
-
-	out := make([][]any, len(funcs))
-	if len(funcs) == 0 {
-		return out, nil
-	}
-
-	parent = getContext(parent)
-	ctx, canFunc := context.WithCancel(parent)
-	defer canFunc()
-
-	ch := make(chan executeResult, len(funcs)) // channel for result
-	var conch chan empty                       // channel for concurrency limit
+	paralleler := new(Paralleler).
+		WithContext(parent).
+		WithConcurrency(concurrency)
 
-	// no concurrency limitation if the value of the number is 0
-	if concurrency > 0 {
-		conch = make(chan empty, concurrency)
-	}
+	paralleler.Add(funcs...)
 
-	go func() {
-		for i := 0; i < len(funcs); i++ {
-			if conch != nil {
-				conch <- empty{}
-			}
-
-			go runTaskInParallel(ctx, i, funcs[i], conch, ch)
-		}
-	}()
-
-	finished := 0
-	for finished < len(funcs) {
-		select {
-		case <-parent.Done():
-			return out, ErrContextCanceled
-		case ret := <-ch:
-			out[ret.Index] = ret.Out
-			if ret.Error != nil {
-				return out, &executionError{
-					index: ret.Index,
-					err:   ret.Error,
-				}
-			}
-			finished++
-		}
-	}
-
-	return out, nil
-}
-
-// runTaskInParallel runs the specified function for Parallel / ParallelWithContext.
-func runTaskInParallel(
-	ctx context.Context,
-	n int,
-	fn AsyncFn,
-	conch chan empty,
-	ch chan executeResult,
-) {
-	childCtx, childCanFunc := context.WithCancel(ctx)
-	defer childCanFunc()
-
-	ret, err := invokeAsyncFn(fn, childCtx, nil)
-
-	if conch != nil {
-		<-conch
-	}
-
-	select {
-	case <-ctx.Done():
-		return
-	default:
-		ch <- executeResult{
-			Index: n,
-			Error: err,
-			Out:   ret,
-		}
-	}
+	return paralleler.Run()
 }
 
 // ParallelCompleted runs the functions asynchronously with the specified concurrency limitation.

paralleler.go

@@ -0,0 +1,136 @@
+package async
+
+import (
+	"context"
+	"sync"
+)
+
+type Paralleler struct {
+	concurrency int
+	ctx         context.Context
+	locker      sync.Mutex
+	tasks       []AsyncFn
+}
+
+func (p *Paralleler) WithConcurrency(concurrency int) *Paralleler {
+	if concurrency < 0 {
+		panic(ErrInvalidConcurrency)
+	}
+
+	p.concurrency = concurrency
+
+	return p
+}
+
+func (p *Paralleler) WithContext(ctx context.Context) *Paralleler {
+	p.ctx = ctx
+
+	return p
+}
+
+func (p *Paralleler) Add(funcs ...AsyncFn) *Paralleler {
+	validateAsyncFuncs(funcs...)
+
+	p.locker.Lock()
+	defer p.locker.Unlock()
+
+	p.tasks = append(p.tasks, funcs...)
+
+	return p
+}
+
+func (p *Paralleler) Run() ([][]any, error) {
+	tasks := p.getTasks()
+	out := make([][]any, len(tasks))
+	if len(tasks) == 0 {
+		return out, nil
+	}
+
+	parent := getContext(p.ctx)
+	ctx, canFunc := context.WithCancel(parent)
+	defer canFunc()
+
+	ch := make(chan executeResult, len(tasks))
+
+	go p.runTasks(ctx, ch, tasks)
+
+	finished := 0
+	for finished < len(tasks) {
+		select {
+		case <-parent.Done():
+			return out, ErrContextCanceled
+		case ret := <-ch:
+			out[ret.Index] = ret.Out
+			if ret.Error != nil {
+				return out, &executionError{
+					index: ret.Index,
+					err:   ret.Error,
+				}
+			}
+			finished++
+		}
+	}
+
+	return out, nil
+}
+
+func (p *Paralleler) getConcurrencyChan() chan empty {
+	var conch chan empty
+
+	if p.concurrency > 0 {
+		conch = make(chan empty, p.concurrency)
+	}
+
+	return conch
+}
+
+func (p *Paralleler) getTasks() []AsyncFn {
+	p.locker.Lock()
+
+	tasks := p.tasks
+	p.tasks = nil
+
+	p.locker.Unlock()
+
+	return tasks
+}
+
+func (p *Paralleler) runTasks(ctx context.Context, resCh chan executeResult, tasks []AsyncFn) {
+	conch := p.getConcurrencyChan()
+
+	for i := 0; i < len(tasks); i++ {
+		if conch != nil {
+			conch <- empty{}
+		}
+
+		go p.runTask(ctx, i, tasks[i], conch, resCh)
+	}
+}
+
+func (p *Paralleler) runTask(
+	ctx context.Context,
+	n int,
+	fn AsyncFn,
+	conch chan empty,
+	ch chan executeResult,
+) {
+	childCtx, childCanFunc := context.WithCancel(ctx)
+	defer childCanFunc()
+
+	ret, err := invokeAsyncFn(fn, childCtx, nil)
+
+	if conch != nil {
+		<-conch
+	}
+
+	select {
+	case <-ctx.Done():
+		return
+	default:
+		ch <- executeResult{
+			Index: n,
+			Error: err,
+			Out:   ret,
+		}
+	}
+}

times.go

@@ -57,51 +57,16 @@ func TimesSeriesWithContext(ctx context.Context, n int, fn AsyncFn) ([][]any, er
 
 // times executes the function n times withe the specified concurrency.
 func times(parent context.Context, n, concurrency int, fn AsyncFn) ([][]any, error) {
-	// the number of concurrency should be 0 (no limitation) or greater than 0.
-	if concurrency < 0 {
-		panic(ErrInvalidConcurrency)
-	}
-	validateAsyncFuncs(fn)
-
-	parent = getContext(parent)
-	ctx, canFunc := context.WithCancel(parent)
-	defer canFunc()
-
-	out := make([][]any, n)
-
-	ch := make(chan executeResult, n)
-	var conch chan empty
+	paralleler := new(Paralleler).
+		WithConcurrency(concurrency).
+		WithContext(parent)
 
-	if concurrency > 0 {
-		conch = make(chan empty, concurrency)
+	tasks := make([]AsyncFn, 0, n)
+	for i := 0; i < n; i++ {
+		tasks = append(tasks, fn)
 	}
 
-	go func() {
-		for i := 0; i < n; i++ {
-			if conch != nil {
-				conch <- empty{}
-			}
-
-			go runTaskInParallel(ctx, i, fn, conch, ch)
-		}
-	}()
-
-	finished := 0
-	for finished < n {
-		select {
-		case <-parent.Done():
-			return out, ErrContextCanceled
-		case ret := <-ch:
-			out[ret.Index] = ret.Out
-			if ret.Error != nil {
-				return out, &executionError{
-					index: ret.Index,
-					err:   ret.Error,
-				}
-			}
-			finished++
-		}
-	}
+	paralleler.Add(tasks...)
 
-	return out, nil
+	return paralleler.Run()
 }